1. Field of the Invention
The present invention relates generally to water treatment systems, and particularly to a scum removal system for liquids wherein a constant flow is maintained into the intake pipe to the geyser pump to draw surface scum from the liquid.
2. Description of the Related Art
Quiescent bodies of impure or contaminated water or other liquids will often have a buoyant layer of material floating thereon, with removal of this buoyant layer being desirable for environmental and/or other reasons. An example of such is often found in the conventional secondary clarifier tank or lagoon in a wastewater treatment plant or facility. The function of such secondary clarifier tanks is to allow the wastewater to become quiescent, so solids may settle out. However, this also allows buoyant materials to rise to the surface of the water, in the form of scum. Such scum can impede discharge performance of pumps in the system, and also generally result in undesirable odors due to the organic decomposition occurring in such scum residue.
Accordingly, various means of scum removal have been developed in the past. Generally, two different principles have been applied to scum removal in wastewater treatment facilities and other situations where scum removal is desired. One such scum removal principle utilizes flat skimmer blades or paddles to remove the scum from the surface mechanically. These mechanical skimmer systems tend to require a fair amount of maintenance and can require considerable power to operate. Another scum removal system utilizes a pneumatic airlift pump to draw the scum into an inlet at the surface of the water. Airlift pumps operate by introducing air into the bottom of a substantially vertical tube disposed within the water, with the air reducing the density of the water or other liquid in the tube and causing the air and liquid mix to rise to the top of the tube where it is ejected from the tube. Airlift pumps have the advantages of simplicity and lack of moving parts in the immersed pump assembly, but produce relatively weak suction for the power required and thus limit the effective surface area that may be treated by such a pump. Such airlift pumps are also prone to clogging under certain circumstances, due to the relatively slow movement of liquid and air through the discharge pipe.
A more recent development has been the geyser pump, which operates by accumulating a relatively large charge of air at the lower end of the pump riser, which results in the air charge being released as a single volume to travel up the riser or discharge pipe of the pump. This increases the periodic lifting force up the discharge pipe to carry an equal amount of liquid (and contaminants, if any) up the discharge pipe with each pulse of air. As in the case of the airlift pump, the rate of flow may be adjusted by adjusting the flow of incoming air to the pump. The relatively powerful lifting action of the geyser type pump is generally used to lift sediment from the bottom of a tank or pond, or to circulate the water or liquid from the bottom of the tank or pond. The relatively powerful action also tends to prevent clogging or buildup of foreign matter within the discharge pipe.
However, the cyclic or pulsing operation of such geyser pumps results in a corresponding cyclic or pulsing flow to the pump inlet. This may be of no great concern where the inlet is submerged, but this pulsing flow has precluded the use of the geyser pump principle for use in scum removal from the surface of a liquid, even though the relatively greater lifting power of the geyser pump provides significant advantages otherwise. Accordingly, there has been no motivation to provide an inlet opening at the water or liquid surface to draw floating scum into the geyser pump for discharge to another area, or to provide vertical adjustment for such an inlet to allow for varying liquid levels.
Thus, a scum removal system for liquids solving the aforementioned problems is desired.